THE MAKING OF A THEORY FACT OR FICTION

Transcription

1 THE MAKING OF A THEORY FACT OR FICTION OVERVIEW This activity supprts the viewing f the film The Origin f Species: The Making f a Thery. Befre and after watching the film, students discuss and evaluate several statements abut Charles Darwin, Alfred Russel Wallace, and the specific evidence that led each f them t the thery f evlutin by natural selectin. This activity serves as an anticipatin guide t fcus students n several key cncepts cvered in the film. It can als be used as a pre- and pst-assessment. KEY CONCEPTS AND LEARNING OBJECTIVES Charles Darwin and Alfred Russel Wallace independently discvered the natural rigin f species and frmulated the thery f evlutin by natural selectin based n distinct sets f bservatins and facts. The natural rigin and evlutin f species prvide scientific explanatins fr bth the diversity and unity f life as well as the sequence f changes fund in the fssil recrd. Natural selectin acts n variatin amng individuals within ppulatins. The differential survival and reprductive success f individuals with different traits causes ppulatins t change frm ne generatin t the next. By cmparing rganisms living tday with the fssil recrds f extinct rganisms, it is pssible t recnstruct an evlutinary histry and infer lines f evlutinary descent. Observatins f the natural wrld raise questins. Scientific explanatins prvide answers t such questins, which can then be tested using additinal bservatins and evidence. Cmmunicatin amng scientists plays a crucial rle in scientific discveries. Students will be able t evaluate claims based n infrmatin and evidence presented in the film; and participate in a cllabrative discussin f their interpretatin f the evidence with their peers. CURRICULUM CONNECTIONS Curriculum AP ( Standards) IB (2009 Standards) NGSS Cmmn Cre Curriculum Tpics 1.A.1, 1.A.2, 1.A.4 5.4, D2, D5 Middle schl: MS-LS2-2, MS-LS2-4, MS-LS4-1, MS-LS4-2, MS-ESS2-3, MS-LS2.A, MS- LS2.C, MS-LS4.A, MS-LS4.B, MS-LS4.C, MS-ETS1.B High schl: HS-LS4-1, HS-LS4-5, HS-LS4.B, HS-LS4.C CCSS.ELA-Literacy.SL.8.1, CCSS.ELA-Literacy.L.8.1, CCSS.ELA-Literacy.L.8.2, CCSS.ELA- Literacy.L.8.6, CCSS.ELA-Literacy.RST.6-8.4, CCSS.ELA-Literacy.RST , CCSS.ELA- Literacy.SL , CCSS.ELA-Literacy.L , CCSS.ELA-Literacy.L , CCSS.ELA- Literacy.L , CCSS.ELA-Literacy.RST , CCSS.ELA-Literacy.SL , CCSS.ELA-Literacy.L , CCSS.ELA-Literacy.L , CCSS.ELA-Literacy.L Updated February Page 1 f 6

2 PROCEDURE Befre Watching the Film 1. Have students wrk in pairs t cmplete the table labeled Befre Watching the Film in the student wrksheet. Let them knw that they are nt suppsed t knw all the answers; at this pint they shuld just recrd their best guess fr each statement based n what they already knw. Ask them t recrd their reasning in the space prvided after each statement. During the Film 2. Have students recrd infrmatin and evidence fr r against each claim as given in the film in the table labeled After Watching the Film. After Watching the Film 3. Have students wrk in pairs t discuss the accuracy f the statements based n infrmatin presented in the film and cmplete the After Watching the Film table. 4. Depending n available time, have a classrm discussin abut each f the statements in the wrksheet and ask students which nes are true and which are false. The key is that students supprt their claims with infrmatin and evidence frm the film. KEY TERMS Darwin, evlutin, fssils, natural selectin, species, variatin, Wallace TIME REQUIREMENT This activity can be mstly cmpleted in ne 50-minute class perid with sme hmewrk. See Teaching Tips fr suggestins n hw t implement the activity in the classrm. SUGGESTED AUDIENCE This activity is apprpriate fr middle schl life science and all levels f high schl bilgy. PRIOR KNOWLEDGE Fr students t be able t answer the questins befre watching the film, it may be helpful fr them t have heard f Darwin and Wallace and be familiar with the terms evlutin and natural selectin. Fr students wh have nt been expsed t these cncepts, the film can serve as an intrductin. TEACHING TIPS One way t structure this activity is fr students t cmplete the Befre table in class (5-10 min.) and then watch the film (30 min.). They can finish the After table the next day in class fllwed by a class discussin. Alternatively, students can cmplete the Befre table in class; watch the film as hmewrk; and cmplete the After table the next day in class, fllwed by a class discussin. Additinal infrmatin abut the events leading up t the frmulatin f the thery f evlutin by natural selectin and f Wallace s and Darwin s lives is prvided in the In-Depth Guide Page 2 f 6

3 ( Cnsider prviding students with a cpy f the backgrund infrmatin in the guide as reading in preparatin t watching the film. After students have cmpleted their wrksheets, have them cnsider additinal questins, such as, What are the key facts and bservatins presented in the film that led Darwin and Wallace t the natural rigin f species in ther wrds, that species descend frm ther species? What is the evidence fr natural selectin as a mechanism f evlutin? Hw did different bservatins, frm different places, lead t the same cnclusins? One pint yu might want t highlight fr students is that the glyptdnt/armadill shwed variatin ver time, whereas the mckingbirds and trtises shwed variatin ver space. Ask students hw each f these types f evidence helped Darwin t reach his cnclusin abut the rigin f species. ANSWER KEY 1. Mst peple living arund Darwin and Wallace s time, including mst scientists, believed in special creatin meaning that Gd created each species n Earth in its present frm. This statement is true. In Darwin s time, mst Eurpeans, including Darwin, believed that Gd had created Earth and all f the rganisms living n it in their current frms. Althugh the ancient Greeks, nn-western cultures, and even sme naturalists in Eurpe had put frth ideas abut evlutin prir t Darwin s and Wallace s wrk, these ntins were nt well frmulated and were marginalized by the prevailing dgma f special creatin. Darwin and Wallace made bservatins f the natural wrld. The evidence they cllected did nt supprt the idea that Gd created species in their present frm and unchanging. Their bservatins and evidence were instead cnsistent with a natural rigin f species. In his autbigraphy, Darwin wrte: The ld argument frm design in nature, as given by Paley, which frmerly seemed t me s cnclusive, fails, nw that the law f natural selectin has been discvered. We can n lnger argue that fr instance the beautiful hinge f a bivalve shell must have been made by an intelligent being, like the hinge f a dr by man. There seems t be n mre design in the variability f rganic beings, and in the actin f natural selectin, than in the curse which the wind blws. (Excerpt frm The Autbigraphy f Charles Darwin: Frm The Life and Letters f Charles Darwin, edited by his sn Francis Darwin.) Sn after the publicatin f On the Origin f Species, mst scientists accepted the ntin that life had evlved, but sme remained skeptical abut natural selectin. Tday, the thery f evlutin by means f natural selectin is a fundatinal principle f bilgy. 2. Befre he set sail n the HMS Beagle, Darwin was training t be a minister. He was asked t jin the vyage t be f cmpany t the Beagle s captain. This statement is true. Befre embarking n his vyage, Darwin was studying t be a minister at Christ s Cllege at Cambridge. During that time he became an enthusiastic naturalist, cllecting beetles and taking classes frm btany prfessr Jhn Stevens Henslw. Henslw was the ne wh passed n the ffer t Darwin t be the naturalist and traveling cmpanin f Cmmander Rbert FitzRy, captain f the HMS Beagle. Darwin s primary jb n the vyage was t prvide upper-class cmpany fr FitzRy, wh wanted a naturalist and a dining cmpanin. Darwin was well suited fr the psitin since he was well educated, an amateur naturalist, and he came frm an aristcratic backgrund. Fr Darwin, the vyage was an extrardinary pprtunity t btain specimens fr his cllectin but he did nt set ut t understand the rigin f species. The missin f the survey ship HMS Beagle was t chart the Suth American cast. Page 3 f 6

4 3. The bservatin that fssils f extinct rganisms are fund where similar rganisms live tday can be explained by the fact that species dn t change ver time. This statement is false. In the film we see that Darwin als discvered the fssil remains f large glyptdnts, which are very similar t, thugh much larger than, present-day armadills. The living tree slths and armadills appeared t have succeeded earlier related species but they are nt the same species. The clustering f similar species in space (that becme different ver time) suggested that each species had descended with mdificatin frm cmmn ancestrs. The fssil recrd was a critical piece f evidence fr Darwin s frmulatin f evlutinary thery. But Darwin realized that the fssil recrd was imperfect. In On the Origin f Species, he predicted that the fssil recrd shuld cntain fssils f creatures with transitinal features. Many transitinal fssils have been identified tday. Lastly, lking nt t any ne time, but t all time, if my thery be true, numberless intermediate varieties, linking clsely tgether all the species f the same grup, must assuredly have existed; but the very prcess f natural selectin cnstantly tends, as has been s ften remarked, t exterminate the parent-frms and the intermediate links. Cnsequently evidence f their frmer existence culd be fund nly amngst fssil remains, which are preserved, as we shall attempt t shw in a future chapter, in an extremely imperfect and intermittent recrd. (Excerpt frm Darwin, On the Origin f Species, Chapter Six: On the Absence r Rarity f Transitinal Varieties, 1859.) 4. Darwin was eager t share his ideas abut evlutin with the rest f the wrld, s he wrte and published his bk, On the Origin f Species, in just tw years after returning frm his vyage n the HMS Beagle. This statement is false. Darwin knew that his ideas abut evlutin wuld be shcking t mst peple because they cntradicted special creatin. S, after returning frm his vyage n the HMS Beagle, Darwin spent years quietly and methdically amassing scientific evidence in supprt f his ideas, while sharing his bservatins and cnclusins with nly a few clse friends. He als published many imprtant papers n his bservatins f the natural wrld, including rganisms such as barnacles, plants, and pigens. It wasn t until 20 years after returning frm his vyage that Darwin finally felt cmpelled t publish On the Origin f Species. He did s because Alfred Russel Wallace had sent him a summary f his wn ideas abut evlutin, natural selectin, and the rigin f species. Wallace had written t Darwin asking him t publish his (Wallace s) thery if he viewed it favrably. Darwin asked tw f his friends and clleagues, gelgist Charles Lyell and btanist Jseph Hker, t view the manuscript. Lyell and Hker decided that the fairest curse f actin wuld be t publish Wallace s essay and Darwin s wrk simultaneusly. They annunced that bth Wallace and Darwin had independently reached the same cnclusins. 5. The bservatin that the mre similar tw species are, the clser they tend t live gegraphically is evidence that species descend frm ther species. This statement is true. The film shws that between 1854 and 1862, Wallace extensively traveled the Indnesian archipelag, cllecting specimens and recrding their lcales. He nticed a clear divide running thrugh the islands with respect t the distributin f species. The birds n ne side were similar t thse fund in Asia, while the birds n the ther side were mre similar t thse fund in Australia. Wallace had effectively discvered the bundary f tw cnverging cntinental plates that ver time had juxtapsed tw distinct island systems. In additin, Wallace nted that certain species f butterflies were nly fund in the Americas, whereas ther types were fund nly in Asia; the same was true fr many ther animals. Thrugh this research, Wallace surmised that species descend frm similar species. In 1855, while in Sarawak n the Malaysian island f Brne, Wallace wrte a paper entitled On the Law Which Has Regulated the Intrductin f New Species n the gegraphic distributin f species. He prpsed that Every species has cme int existence cincident bth in time and space with a pre-existing clsely allied species." Wallace described that species have evlved ver time, with sme species becming extinct and new species evlving frm earlier frms. Wallace is ften referred t as the father f mdern bigegraphy. Page 4 f 6

5 6. The finger bnes inside manatee and whale flippers are evidence that these living species are mdified frms f lder species. This statement is true. The film shws that Wallace wndered why imperfectins, such as finger bnes in whale flippers, existed. Whales dn t grasp and manipulate bjects with their flippers, s why wuld they need finger bnes? Why wuld seemingly useless structures be present if every species was specially created? Bth Wallace and Darwin searched fr a scientific explanatin fr these questins. They cncluded that the presence f such structures was cnsistent with the thery f descent with mdificatin, as the finger bnes in whale flippers represented mdified frms f structures present in a cmmn ancestr. Often mdified frms als have mdified functins. Fr example, the human arm, whale s flipper, and bat s wing are adapted fr different purpses but share the same basic bne structure, indicating that these rganisms descended frm a cmmn ancestr. 7. Darwin and Wallace made bservatins f the natural wrld, including that individuals within a species have variatins that affect hw well they cmpete fr limited resurces. This statement is true. The film shws that Wallace realized that individuals within a species cmpete fr survival. Because individuals within a species vary in traits, in a given envirnment thse individuals with traits that prvide them with an advantage are mre likely t survive and prduce mre ffspring. Over time, these advantageus traits accrue in the ppulatin. Darwin independently made similar bservatins. In 1798, Thmas Malthus, an English clergyman and ecnmist, published An Essay n the Principle f Ppulatin. The central theme f this wrk was that human ppulatin grwth wuld always exceed fd supply grwth, thus creating nging states f hunger, disease, and struggle. He bserved that unless kept in check, human ppulatins wuld duble every 25 years. Malthus wrte: I think I may fairly make tw pstulata. First, That fd is necessary t the existence f man. Secndly, That the passin between the sexes is necessary and will remain nearly in its present state. These tw laws, ever since we have had any knwledge f mankind, appear t have been fixed laws f ur nature, and, as we have nt hithert seen any alteratin in them, we have n right t cnclude that they will ever cease t be what they nw are. Assuming then my pstulata as granted, I say, that the pwer f ppulatin is indefinitely greater than the pwer in the earth t prduce subsistence fr man. (Excerpt frm Malthus, T. An Essay n the Principle f Ppulatin, Chapter 1, 1798.) Bth Darwin and Wallace read Malthus and realized that plant and animal ppulatins have the same ptential as human ppulatins t increase rapidly unless kept in check by predatrs, diseases, and limited resurces. On this tpic, Darwin wrte: Can it, then, be thught imprbable, seeing that variatins useful t man have undubtedly ccurred, that ther variatins useful in sme way t each being in the great and cmplex battle f life, shuld smetimes ccur in the curse f thusands f generatins? This preservatin f favurable individual differences and variatins, and the destructin f thse which are injurius, I have called Natural Selectin, r the Survival f the Fittest. (Excerpt frm Darwin, On the Origin f Species, Chapter IV. Natural Selectin, 1859.) 8. Darwin and Wallace used DNA evidence t supprt their ideas abut evlutin and hw species are related. This statement is false. Darwin and Wallace based their thery f evlutin n bservatins f the natural wrld mainly f the variatin in physical traits amng individuals within species, similarities between animals in the fssil recrd and existing species, and the gegraphical distributins f related species. Darwin and Wallace did nt knw hw heredity wrked, and genes had nt yet been discvered r defined. At arund the same time as Darwin s and Wallace s vyages, Gregr Mendel s experiments with pea plants shwed the basic mechanisms f heredity. Mendel prvided the famus ratis f variatins passed n frm ne generatin t the next Page 5 f 6

6 that are the basis fr what tday we knw as Mendel s principles. Darwin never read Mendel. It was nt until the next century, arund 1900, when new researchers, including Thmas Hunt Mrgan, wrked with Mendel s discveries and fund that natural selectin and heredity culd be brught harmniusly tgether. REFERENCES Darwin, C.R The Autbigraphy f Charles Darwin N. Barlw, Ed. New Yrk: W.W. Nrtn. Darwin, C.R On the Origin f Species. Lndn: Jhn Murray. Wallace, A.R On the law which has regulated the intrductin f new species. Annals and Magazine f Natural Histry 2nd Ser. 16: Wallace, A.R Darwinism. Lndn: Macmillan. AUTHORS Written by Mary Clvard, Cbleskill-Richmndville High Schl (retired), and Laura Bnetta, PhD, HHMI Edited by Dennis Liu, PhD, HHMI, and Stephanie Keep, cnsultant; Cpyedited by Linda Felac Reviewed by Paul Beardsley, PhD FIELD TESTERS Angeliki Aravantins, Jhn Bwne High Schl, NY; Kathy Cahn, La Plata High Schl, NY; Mrira Cahdzutk, St. Jhn the Baptist DHS, NY; Linda Cita, St. Jhn the Baptist DHS, NY; Jerry Citrn, Stuyvesant High Schl, NY; Rsari Cuarters, Belmnt Preparatry High Schl, NY; Lilleen Ferrar, Linden Academy, NY; Dnald Kirkpatrick, Marin High Schl, SC; Jack Saffer, Central Islip High Schl, NY. Page 6 f 6